The present invention relates to a temperature sensing apparatus and particularly to such an apparatus which is adapted for sensing surface temperature of another structure.
Temperature sensing and control systems may employ a variety of electrically based transducers. Generally, available transducers incorporate resistance sensitive elements, thermocouple elements or semi-conductor elements, all of which produce a change in electrical characteristic in response to a sensed temperature change. A readout device, such as a digital reading thermometer, provides accurate conversion of the signal from the sensor apparatus. In those applications where the transducer is immersed within the media which changes in temperature, temperature-related-output can be obtained with a high degree of accuracy. For surface temperature measurement, the sensor is constructed to respond to an engagement of the transducer with the surface. With existing devices, however, significant difficulties have been encountered in obtaining an accurate detection of surface temperatures. Various factors contribute to the inaccuracies in the results. Some of the most significant factors include poor thermal contact between the sensor element and the surface, thermal non-equilibrium between the sensor element and the surface, unacceptable levels of heat extraction by the sensor or surface from the opposite member, and finally thermal radiation within the sensor unit, as such. Generally, the inaccuracies associated with prior art contact surface measurement devices are related to the design and construction of the sensor apparatus, as such, including the physical construction as well as the response materials or elements and their support or mounting. For example, unless the configuration of the sensing element and the surface to be measured are the same, appropriate contact or engagement will probably not be obtained. The thermal capacity, mass and transfer characteristics of the sensor unit, associated coupling elements or mediums for establishing engagement with the surface may, of course, significantly effect the accuracy of the readout. Thus excessive mass, a low coefficient of thermal conductivity and the like will normally introduce inaccuracies into the response characteristic and readout.